US scientists believe they have made a discovery which could mean a cure for more diabetic patients in the future.
Transplant cures can mean an end to injections
Some patients have already been cured by islet cell transplants, but a major obstacle is a shortage of donor pancreases to harvest the cells from.
Now National Institute of Health scientists say they have found a way to make more of the cells required.
They told the online edition of Science that they used a serum derived from cows to help in their reproduction.
People with Type 1 diabetes need to inject insulin to keep their blood sugar under control.
This is because the islet cells in their pancreas, whose job it is to make insulin, have been destroyed.
Replacing the loss with islet cells from donors can cure the condition.
However, a large number of islet cells are needed and there are too few donors to meet demand.
Stem cells - very primitive cells that have the capability to become any cell in the body - have offered some hope, but again it is difficult to produce enough islet cells from stem cells.
Dr Marvin Gershengorn and colleagues at the National Institute of Diabetes and Digestive Kidney Diseases looked at a way of solving this problem.
They removed islet cells from pancreases donated by people who had died.
They then exposed the islet cells to a medium containing a substance called foetal bovine serum.
This serum, derived from cows, appeared to encourage the islet cells to change into more primitive cells that were the predecessors of islet cells.
Although these human islet-derived precursor cells, or hIPCs, do not themselves produce insulin, they are able to replicate easily.
This means it is possible to get large numbers of hIPCs in a relatively short time period - almost a billion-fold increase in 90 days.
They are different from stem cells because they are more developed and can only go on to become islet-like cells, which they did in the US trials.
These islet-like cells showed many of the characteristics of the original islet cells and were capable of producing small amounts of insulin.
The researchers said their findings were exciting but in their early stages.
Dr Gershengorn said: "This is a step forward in the field, but we are still a long way from using this knowledge to develop therapies for diabetes.
"For one thing, these differentiated cells do not function as well as the original cells.
"They don't produce as much insulin and they are not as adaptable to changes in the environment.
"For another thing, we grew these cells in a culture that is not optimal for use in humans, so we are not ready to transplant these cells into people. Still, I'm encouraged."
He said they hoped to be able to overcome some of these barriers in the near future.
Jo Brodie, islet project co-ordinator at Diabetes UK, said: "This research is useful in helping us to understand the process involved in islet development and could lead to advances in islet cell transplants for people with Type 1 diabetes.
"We await with interest further results in this area."